Vacuum pump and rotating body for vacuum pump

Abstract

An object is to prevent backflow of particles during discharging. The vacuum pump includes: a casing having an inlet port and an outlet port; a stator column provided upright inside the casing; a rotating body having a shape surrounding an outer circumference of the stator column; and a magnetic bearing configured to magnetically levitate and support a rotating shaft of the rotating body, with the vacuum pump being configured to suck gas from the inlet port and exhaust the gas from the outlet port by rotation of the rotating body, wherein a projection portion for discharging an electric charge carried on the rotating body is provided at at least one of a first position formed on a back surface side of the rotating body, a second position formed on a bottom surface side of the rotating body, and a third position formed in an intermediate point of a flow passage of the gas of the rotating body.

What is claimed is: 
     
       1. A vacuum pump comprising:
 a casing having an inlet port and an outlet port; 
 a stator column provided upright inside the casing; 
 a rotating body having a shape surrounding an outer circumference of the stator column; and 
 a magnetic bearing configured to magnetically levitate and support a rotating shaft of the rotating body, 
 the vacuum pump being configured to suck gas from the inlet port and exhaust the gas from the outlet port by rotation of the rotating body, wherein 
 a projection portion for discharging an electric charge carried on the rotating body toward the stator column is provided at a first position formed on a surface in a back surface of the rotating body, with the surface facing an upper end surface of the stator column. 
 
     
     
       2. The vacuum pump according to  claim 1 , wherein the projection portion is set to have a height that does not cause the projection portion to come into physical contact with an upper end surface of the stator column even in a state in which the rotating body is not magnetically levitated. 
     
     
       3. The vacuum pump according to  claim 1 , wherein a purge gas flow passage, in which purge gas flows, is formed between the back surface of the rotating body and the upper end surface of the stator column. 
     
     
       4. The vacuum pump according to  claim 1 , wherein the projection portion has a pointed shape. 
     
     
       5. The vacuum pump according to  claim 1 , wherein the projection portion has a gas release hole. 
     
     
       6. The vacuum pump according to  claim 1 , wherein
 the projection portion is provided in plurality, and 
 the plurality of projection portions are located at a same radius about an axis of the rotating body and located at mutually regular intervals in a rotational direction with respect to the axis of the rotating body. 
 
     
     
       7. A vacuum pump comprising:
 a casing having an inlet port and an outlet port; 
 a stator column provided upright inside the casing; 
 a rotating body having a shape surrounding an outer circumference of the stator column; and 
 a magnetic bearing configured to magnetically levitate and support a rotating shaft of the rotating body, 
 the vacuum pump being configured to suck gas from the inlet port and exhaust the gas from the outlet port by rotation of the rotating body, wherein 
 a projection portion is provided at a second position formed on a bottom surface of a cylindrical portion forming a lower portion of the rotating body and is configured to discharge an electric charge, carried on the rotating body, toward a base portion forming a bottom portion of the casing, and 
 the projection portion is set to have a height that does not cause the projection portion to come into physical contact with the base portion even in a state in which the rotating body is not magnetically levitated. 
 
     
     
       8. The vacuum pump according to  claim 7 , wherein a purge gas flow passage, in which purge gas flows, is formed between the bottom surface of the cylindrical portion and the base portion. 
     
     
       9. A vacuum pump comprising:
 a casing having an inlet port and an outlet port; 
 a stator column provided upright inside the casing; 
 a rotating body having a shape surrounding an outer circumference of the stator column; and 
 a magnetic bearing configured to magnetically levitate and support a rotating shaft of the rotating body, 
 the vacuum pump being configured to suck gas from the inlet port and exhaust the gas from the outlet port by rotation of the rotating body, wherein 
 the rotating body includes, in multiple stages, a plurality of rotor blades, 
 the casing includes, in multiple stages, a plurality of stator blades provided in a staggered manner with the plurality of rotor blades, and 
 a projection portion is provided at a third position formed on a surface of a rotor blade among the plurality of rotor blades that is located on a downstream side, and is configured to discharge an electric charge carried on the rotating body toward a stator blade among the plurality of stator blades that is located in one of the stages located above and under the rotor blade that is located on the downstream side.